Turn localized_function decorator into class

[ChanceNCounter]

When finished, this should speed up function calls by a considerable margin (in computing terms.) Right now, the function checks the validity of its run_own_code_on parameter every time you call a localized function. This was a tradeoff, but it's particularly egregious considering that the parameter is almost always [None].

By turning the decorator into a class, we can run that check once, when the class is instantiated. It may, however, substantially increase the memory footprint - I haven't checked - which would partially obviate the memory gains from the 0.3 refactor (however, it's still whittled down to just the languages the user is... using...)

[ChanceNCounter]

This might be better accomplished when the localized modules are crawled at load time, which probably wouldn't affect the memory footprint.